GROWTH OF TISSUES OF THE CHICK EMBRYO 65 



gation was completed. In the present communication the tech- 

 nique of preparing the tissues and the culture media and the obser- 

 vations upon the growth of the isolated embryonic tissues of 

 the chick embryo, will be taken up, leaving for future work the 

 full analysis of the conditions which affect this growth. 



MATERIALS 



Chick embyros are of special advantage, not only on account 

 of the ease of obtaining them throughout the year, but also on ac- 

 count of the importance of having a warm-blooded animal for 

 this study. 



Secondly, the tissues of these embryos receive their nutrition 

 at an early age from an extracellular yolk through a well estab- 

 lished vascular system. The removal of the tissue from the embryo 

 interrupts its vascular connections and removes all the nourishing 

 agents of the yolk. The development, therefore, of such a tech- 

 nique offers not onlj^ the opportunity for the study of tissue growth, 

 as originated by Harrison, but also gives an opportunity for the 

 study of cell nutrition. 



For the work at hand embryos of sixty hours of incubation 

 were found most suitable. At this stage, according to Held ('09), 

 some peripheral nerves have formed. However, there are many 

 neuroblasts which have not begun their differentiation. 



At a culture medium blood plasma prepared from the blood of 

 adult chickens was substituted for the lymph used by Harrison, 

 and in this way the chief difficulties encountered by Harrison 

 were overcome. This medium was easily obtained, and the clots 

 were firm and uniform, giving a greater range of control. Such 

 preparations could be readily preserved and stained by any of 

 the usual histological methods. 



The Jouknal of Experimbntax Zoology, Vol. 10, No. 1 



